The present invention relates to anti-friction bearings adapted for use in a vacuum, for example, in rotating amode X-ray tube assembly, vacuum evaporation apparatus and like vacuum apparatus or in devices designed for travel in space.
Bearings for use in a vacuum involve difficulty in lubrication with oil or grease, so that in the prior art bearing components, such as rolling elements, are coated with a solid layer of a metal with lubricating property, molybdenum disulfide or like lubricant for lubricating the surface to be subjected to rolling friction or sliding friction. Generally such metal coatings are formed by the usual ion plating method as disclosed, for example, in Published Unexamined Japanese Patent Application No. 19840/1977.
However, the coatings formed by the conventional ion plating method have the drawbacks of being low in adhesive strength and therefore liable to separation in a short period of time during the operation of the bearing and giving a very short life to the bearing.